Industrial electric motors for high rotation speeds, for example for a turbocompressor of an industrial installation, contain a solid rotor which comprises a steel body and an integrated cage made of copper parts, for example rings and rods. The rods are in this case inserted into grooves of the metal core, which extend in the axial direction, and are electrically connected to one another by short-circuit rings likewise made of copper. Such electric motors are also used for the compression of chemically aggressive process gases in industry, which may attack the copper parts so that the working life of these electric motors is reduced.
In order to protect the sensitive motor parts, it is known from WO 2005/124973 A1 to apply a metallic protective layer made of Inconel onto the rotor. Inconel is a registered trademark of Special Metals Cooperation, New Hartford, N.Y., USA. The protective layer covers the copper parts and thus protects them from corrosive gases.